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Discussion Starter · #1 · (Edited)
O. K. - I'm a real novice when it comes to rear axle ratios and transmissions. I do know that the larger the number (4.11:1) , the higher the engine RPM's at a given speed and the smaller the number (2.56:1) the lower the engine RPM's at a given speed.

My 57 was originally powered by a 6 Cyl with a 3 speed manual transmission. The engine in it now is a 1963 283 with a 1963 Power Glide.

I think the rear axle is original to the car, which means it has a ratio of 3.55 to one, which I have not yet verified.

The 57 power glide axle had a ratio of 3.36 to one.

Questions:

1 - How bad is the 3.55 to one axle going to affect gas mileage/drive ability?
2 - Should I get a 3:36 to one power glide center section?
3 - Would a 2:56 to one get better gas mileage and would it lug the engine down too much? Not really wanting to drag race just cruse around.
4 - Will I have to change the odometer cable drive gears if I go to either of the lower number axle center section?

Would like to keep cruse RPM's under 2300

Thanks for suggestions and information on which way to go.
 

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I guess the answer depends on what you want to do with the car. The 283 is a nice rugged dependable motor but does not have a lot leg to them (to get them to run really well traditionally required high compression, lots of cam and some RPMs). So, in stock form, the 283 will simply run better stoplight to stoplight and all around town with the 355 gear, which in my opinion is a great all around gear. If you are really concerned with gas mileage, then the lower numerical ratios are what you want but lower gears come with their own little warts like the car will be somewhat of a slug to drive around town as it will be lacking a good bit of gear multiplication in low, and if the gear ratio is too low, the car will be worse then a slug, and the auto trans may lug in high gear. Just my thoughts.
 

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Believe original 3 speed stick shift car would have a rear end about 3:70. Best way to tell is to jack the rear end up turn both wheels around one revolution while counting turns of drive shaft.

An overdrive trans would be another solution.
:anim_25:
 

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The 63 glide probably already has the correct speedo gears for 3.36 that it was in the original car. If so, your speedo probably reads a little faster than your actual speed. If it was mine, I wouldn't spend the time and money to change up one ratio. I just slow down and enjoy the drive longer and safer.
 

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Yes. Verify your current ratio. There are numbers on it you can verify on the first few pages of the shop manual
 

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3.36 gears would drop the RPMs by only 5% or so. That means 3,000 RPM at xx mph on the highway would become 2,850 RPM.

A 700R4 trans with your 3.55 may be your best bet, with a lower 1st gear than your PG, and a .70 4th gear.
 
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